JPS6225897A - Method and apparatus for controlling four-phase stepping motor - Google Patents

Abstract

PURPOSE:To inhibit the vibration of a rotor in case of holding, and to prevent the pull out by making low currents flow through field coils of the other two phases and bringing the field coils to three-phase excitation in one-phase exciting section in W1-2 phase excitation. CONSTITUTION:A memory element 2 each outputs signals H, L to first-eighth outputs 20-27 in response to an output from a binary counter 1. A PWM control circuit 6 and a switching transistor driving circuit 3 are operated in response to the signal, and the currents of several field coil are controlled. One phase exciting section in conventional W1-2 phase excitation can be brought to three-phase excitation by respectively making a first current level to flow through field coils at other two phases at that time.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a four-phase step motor with W (double) 1-2
The present invention relates to excitation of a field coil that suppresses rotor vibration when driven by phase excitation.

[Conventional technology]

The conventional step motor driving method is
As shown in Publication No. 278, 1-phase excitation, 2-phase excitation, 1
- There are various excitation methods such as two-phase excitation, and methods of simultaneously exciting multiple phases such as two-phase excitation and 1-2 phase excitation are collectively called polyphase excitation.

In addition to the above-mentioned two-phase excitation and 1-2 phase excitation, this multi-phase excitation includes step-like current flow to the field coils of each phase of the motor, as shown in Japanese Patent Laid-Open No. 58-69499. There is a method of increasing the angular accuracy of the step motor and reducing torque ripple by driving the step motor by changing the angle. °This driving method is generally called microstep driving.

The Wl-2 phase excitation, which is the excitation method according to the present invention, is considered to be a type of multiphase excitation, and can be thought of as setting the current value flowing through the field coil in two stages in microstep drive. .

This Wl-2 phase excitation is shown in Japanese Patent Laid-Open No. 58-9597. FIG. 6 shows an embodiment of the Wl-2 phase excitation drive circuit described above.

Further, this figure is a four-phase VR type step motor of a unipolar excitation type, and only two phases of the drive section are shown. In the figure, 1 is a 4-bit binary counter that counts and outputs the number of pulses when a drive command pulse is supplied to the input terminal 14, and the output is input to the memory element 2 (usually a ROM). And λru.

The memory element 2 includes the first to eighth 8th elements of 20 to 27.
outputs two outputs. Here, the output of binary counter 1 (
According to the truth table shown in Table 1,
H and L signals are output to the first to eighth outputs 20 to 27 of the memory element 2 . However, 4th. The fifth output 24.25 is undefined.

In addition, numerals 3 and 4 are driving circuits for the switching transistor 8.9 and the 4.degree. second output 2 of the memory element 2, respectively.
3.21, and has the function of making the transistors 8 and 9 conductive if the signal from the memory element 2 is H, and shutting them off if it is L.

5 is the current value flowing through each phase of the step motor as PWM (
This is a triangular wave oscillation circuit for pulse width modulation (pulse width modulation) control.

6 is a PWM (pulse width modulation) control circuit, into which the triangular wave from the triangular wave oscillation circuit 5 is input. And memory element 2
In response to the H9L signal of the signal from the eighth output 27 of , two reference voltages are obtained respectively.

Next, the voltage of the current detection resistor I2 is fed back, compared with the reference voltage, and the error signal (voltage) is compared with the triangular wave to obtain the necessary duty ratio corresponding to the signals H and L. , controls the base of the current control transistor 7,
The current flowing through the field coils 10° and 11 of each phase is kept constant. When the signal is low, the current flowing through the current control transistor 7 is about half that of the signal H.

7 is a current control transistor, the emitter is connected to the power supply terminal,
The collector is connected to one end of field coils 10.11 of two of the four phases.

The other ends of the field coils 10 and 11 are connected to a resistor 12 via the collectors and emitters of switching transistors 8 and 9, respectively.

To explain the operation of the circuit described above, clock input terminal 1
4, when a rectangular wave of a certain frequency is input, the first to
The signals shown in Table 1 are output from the eighth outputs 20-27.

Based on this signal, the PWM control circuit 6 and the switching transistor drive circuit (3, 4) operate, and as shown in FIG. 7, current is supplied to the field coils of each phase (1 to 4). It will happen. Also, 1 to 16 in Figure 7
The numbers correspond to the count numbers θ to 15 in Table 1, respectively. The energization of the field coil in FIG. 7 is called Wl-2 phase excitation.

Here, the frequency of the rectangular wave input from the clock input terminal 14 determines the pulse rate for driving the step motor; if the frequency is high, the step motor will rotate at high speed, and if the frequency is low, it will rotate at low speed.

[Problem that the invention seeks to solve]

However, in the conventional system described above, as shown in FIG.
1, 5.9.13) in the figure always exists, for example,
When the step motor is held (stopped) in this part, the field coil is only performing one-phase MJJ magnetization, which causes a problem that the rotor vibrates large and is likely to become out of synchronization.

[Means for solving problems]

Each phase from the first phase to the fourth phase has one period with 16 sections, and the first current level is applied for two sections, and then the first
A method for controlling a four-phase step motor in which a second current level that is larger than the current level is applied for 5 sections, the first current level is applied for 2 sections, and the remaining 7 sections drive the energized whirlpool motor. It is to be.

[Effect]

In the 1-phase excitation part in the conventional Wl-2 phase excitation,
The first current level is applied to the other two-phase field coils to provide three-phase excitation.

〔Example〕

The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 1 shows a first embodiment of a control device for a four-phase step motor according to the present invention. In the figure, the same reference numerals as in FIG.
Only phase components are shown. In addition, the 4-phase step motor is
It is a VR type with a plurality of salient poles on the rotor.

Then, each phase of the four-phase field coil is independently connected to a drive circuit 3, PWMilJ? 11 circuit 6, current control transistor 7, switching transistor 8, field coil 10
, and a resistor 12 are connected to control the current value of the field coil.

In addition, the memory element 2 outputs H to the first to eighth outputs 20 to 27 of the memory element 2, respectively, according to the truth table shown in Table 2, in accordance with the output (count number) of the binary counter 1.
, L signals are output.

Below margin Here, the output of the memory element 2 forming the first means.

24 to 27 are each connected to the PWM control circuit 6, and generate a first level signal (L signal) for 11 periods.
After that, a second level signal (H signal) is generated for 5 sections,
Signals are generated with a shift of four sections.

Further, the outputs 20 to 23 of the memory element 2 constituting the second means
is a transistor 8 that turns on and off the field coil 10;
are connected to drive circuits 3 for driving the bases of O
The N signal (H signal) is generated for 9 periods, and then the OFF signal (
L signal) is generated for 7 sections, and the signals are generated with a shift of 4 sections for each section. Furthermore, the beginning of each ON signal (H signal) corresponds to the 10th section of the 11 sections of the first level signal obtained by the first means.

To explain the operation of the above-mentioned circuit in detail, this circuit can control the current of each phase independently, so in response to a rectangular wave of a certain frequency input from the clock input terminal 14,
Since the signals stored in the memory element 2 are output cyclically, the third means P
The WM control circuit 6 and the switching transistor drive circuit 3, which is a semiconductor switching element, operate, and each of the four-phase (first phase, second phase, third phase, and fourth phase) field coils is supplied with the timing shown in FIG. The current will be switched.

For example, if the output of counter 1 (number of counters) is 5,
The memory element 2 outputs the data at 50 o'clock shown in Table 2.

When this data is output, in the PWM control circuit 6 connected to the output terminals 24 to 27, for example, the output terminal 27
In the case where the voltage is connected to Compared with the triangular wave of the triangular wave oscillation circuit 5, a rectangular wave having a necessary duty ratio is obtained, the base of the current control transistor 7 is controlled, and the current flowing through the field coil 10 is set to the second current level. On the other hand, for those connected to output terminals 24 to 26,
As described above, a rectangular wave with a small duty ratio is obtained by the signal No. 26, and the current flowing through the field coil 10 is set to the first current level via the current control transistor 7. At this time, the first current level is set to about 0.41 times the second current level. and,
The triangular wave oscillation circuit 5, the PWM control circuit 6, and the current control transistor 7 constitute a third means.

Furthermore, in the switching transistor drive circuit 3 connected to the output terminals 20 to 23 of the memory element 2, the switching transistor 8, which is connected to the output terminal 22.23, is connected to the ONL, output terminal 20.21. However, the switching transistor 8 is turned off.

Through the above operations, the current in each phase is controlled to the state shown in No. 6 in FIG. 2. In other words, the first phase field coil receives the second current level, and the second phase field coil receives the first current level.
Current levels flow respectively, and no current flows through the third-phase and fourth-phase field coils.

Then, each time a rectangular wave is input to the clock input terminal 14, it is counted, and as shown in Table 2, it is sequentially output to the outputs 20 to 27 of the memory element 2 according to the count number. Accordingly, current flows through the first to fourth phase field coils as shown in FIG. 2.

Here, in Figure 2, one cycle is divided into 16 sections,
In each phase, the first current level lasts for two periods, then the second current level lasts for five periods, then the first current level lasts for two periods, followed by seven unenergized periods.
The section will continue.

Each phase is energized at intervals of four intervals.

As shown in Fig. 7 in the conventional case, 1°5.9
．． In the part 13, there is a case of one-phase excitation, whereas in the part shown in FIG. 2 according to the present invention, 1, 5, 9, .
13 is 2 at the first current level to the field coils of the other two phases.
There is a phase flow, and three-phase excitation is performed.

Further, FIGS. 3 and 4 show the vibration of the rotor when the step motor is held at any part of 1, 5, or 9.13, and show the present invention and the conventional method, respectively. Here, the horizontal axis shows time, and one section is 8ms e
c, and the vertical axis indicates the number of steps in the vibration of the rotor, with one section being 10 steps. In addition, the step motor at this time has a rectangular wave input manually to the binary counter 1 of 2000 p 1) S (pul
se /5econd).

Therefore, as can be understood from FIGS. 3 and 4, the present invention can eliminate vibrations of the rotor as much as possible and will not cause out-of-synchronization.

Furthermore, when implementing the excitation method of the present invention, for example, the first phase and third phase current levels are the same in 1 of FIG. It has no effect on accuracy.

Furthermore, when compared with the conventional method, l in Fig. 2,
5.9.13, the current consumption in this excitation state increases because the current is changed from one phase to three phase excitation compared to the conventional one, but this increase is the average value compared to other excitation states in the motor operating state. Therefore, the increase in current consumption is small and has almost no effect on efficiency, etc.

In the second embodiment shown in FIG. 5, unlike the first embodiment shown in FIG. 1, a PWM control circuit 6, a current control transistor 7, and a current detection resistor 12 are required for each phase. On the other hand, the above circuits and elements can be formed in two phases, one each.

In addition, the AND circuit 1 outputs 23 and 21 of the memory element 2.
The output of the AND circuit 15 is connected to a detected current value switching circuit 16, and the output of this detected current value switching circuit 16 is input to the PWM control circuit 6.

Further, the memory element 2 outputs H signals to the first to eighth outputs 20 to 27 of the memory element 2, respectively, according to the truth table shown in Table 3 below.

The output 24.25 is undefined.

Margin below And the operation of the detection current value switching circuit 16 is that when an H signal is received from the AND circuit 15, the voltage across the current detection resistor 12 is halved within this circuit and sent to the PWM control circuit 6. When the signal from the ANI) circuit 15 is L, it functions to send the voltage as it is. And AND circuit 1
5, a detection current value switching circuit 16, and a resistor 12 constitute a fourth means.

This circuit is composed of, for example, a digital switch and an operational amplifier.

In the above circuit configuration, how this circuit operates will be explained below.

Since the basic operation of the circuit is the same as that shown in FIG. 1, the current value setting during three-phase excitation, which is a feature of the present invention, will be explained in detail.

For example, when controlling number 9 in FIG. 2, memory element 2 outputs address 8.

Based on this signal, the PWM control circuit 6 and the switching transistor drive circuit 3.4 operate, and a voltage of 1/2 of the voltage from the contact detection resistor 12 is detected at the output terminal 21.23 of the memory element 2. From the switching circuit 16, PWM
It will be output to the control circuit 6. That is, the current flowing through the current control transistor 7 is set to twice the first current level, and the current flowing through the field coil 10.11 is set to the first current level.

In other words, switching transistors 8 and 9 are turned on at the same time.
At this time, the resistance values of the field coils 10 and 11 of each phase are equal, so in the end, the field coils to and it of each phase have the following values.
The current level becomes half of the first current level, which is twice as high as that of the first current level, and a current of an intermediate value (first current level) flows as shown at No. 9 in FIG.

Although the above embodiment uses a VR type four-phase step motor, a PM type four-phase step motor using a permanent magnet in the rotor may also be used.

〔Effect of the invention〕

As described above, in the present invention, the 1-phase excitation part in the conventional Wl-2-phase excitation is made into 3-phase excitation by flowing the first current level to each of the other 2-phase field coils. This has the excellent effect of suppressing the vibration of the rotor and preventing out-of-synchronization when the step motor is held.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram showing a first embodiment of the step motor control device of the present invention, FIG. 2 is a characteristic diagram showing the current level flowing through the field coil with respect to the excitation coil of each phase in the present invention, and FIG. The figure is a characteristic diagram showing the vibration of the rotor when the step motor of the present invention is held, FIG. 4 is a characteristic diagram showing the vibration of the rotor when the step motor is held in the conventional method, and FIG. 5 is the characteristic diagram showing the vibration of the rotor when the step motor of the present invention is held. 6 is an electric circuit diagram showing a conventional step motor control device, and FIG. 7 is a field diagram for the excitation coil of each phase in the conventional method shown in FIG. 6. FIG. 3 is a characteristic diagram showing the level of current flowing through a coil. 1... 4-bit binary counter, 2... Memory element forming first and second means, 3.4... Drive circuit, 5, 6.7... Each forming third means. triangular wave oscillation circuit, PWMllji circuit, current control transistor, 8, 9... switching transistor forming a semiconductor switching element, 10.11... field coil,
12...Resistance. Representative Patent Attorney Takashi Okabe

Claims (3)

[Claims] (1) Each phase from phase 1 to phase 4 has one period.
The first current level is applied for 2 periods, then the second current level, which is larger than the first current level, is applied for 5 periods, and the first current level is applied for 2 periods, and the remaining current level is applied for 2 periods. The seventh section is not energized, and the first
A method of controlling a 4-phase step motor in which each phase from phase to fourth phase is repeatedly energized in four intervals to drive the step motor. (2) In a four-phase step motor having a field coil wound in four phases and a rotor rotatably provided on the inner periphery of the field coil, a command pulse that issues a drive command to the step motor. and the first level signal is set to 1 according to the count number of this command pulse.
a first means for generating a second level signal for one period, then generating a second level signal for five periods, repeating the above 16 periods, and simultaneously generating four signals shifted by four periods each; Accordingly, an ON signal is generated for 9 periods corresponding to the 10th period among the 11 periods of the first level signal obtained by the first means, and then an OFF signal is generated.
A second signal that generates a signal for 7 sections, repeats the above 16 sections, and simultaneously generates 4 signals shifted by 4 sections each.
means for setting the current flowing through the field coils of each phase to a first current level using a first level signal obtained by the first means, and setting the current flowing through the field coils of each phase to a first current level using a second level signal; a third means for setting a second current level larger than the current level; and a third means for conducting with an ON signal obtained by the second means, causing current to flow through the field coil, and cutting off with an OFF signal; A step motor control device equipped with a semiconductor switching element that interrupts the current flowing through the field coils of each phase. (3) It has two field coils connected in parallel,
In a four-phase step motor with a rotor rotatably provided on the inner periphery of this field coil, the first level signal is set to 3 depending on the command pulse that commands the drive of the step motor and the count number of this command pulse.
A second level signal is generated for five intervals, and then a second level signal is generated for five intervals.
a first means for repeating the eight sections and simultaneously generating two signals shifted by four sections; Corresponding to the second section of the level signal, generates an ON signal for 9 sections, then generates an OFF signal for 7 sections, repeats the above 16 sections, and simultaneously generates 4 signals shifted by 4 sections each. a second means; setting the current flowing through the field coils of each phase to a first current level using a first level signal obtained by the first means; and setting the current flowing through the field coils of each phase to a first current level using a second level signal; a third means for setting a second current level larger than the first current level; and an ON signal obtained by the second means is used to conduct a current, and an OFF signal causes a current to flow through the field coils of each phase. Semiconductor switching elements that cut off the currents flowing through the respective phase field coils, and when both the pair of parallel-connected semiconductor switching elements are energized, the currents flowing through the pair of field coils are set to a first current level. A step motor control device, comprising: fourth means for setting twice the number; and a step motor control device.